The present invention is directed to both method and apparatus for brooding fish. The present invention has specific application for mouthbrooding fish.
Fish employ a variety of methods for brooding their young. Such methods include, in a first extreme, simply scattering eggs on the bottom and leaving them never to return. The mouthbrooder species are at the other extreme in that these fish carry their eggs and hatched young around in their mouths. In the case of the female mouthbrooder, the eggs are laid in a convenient location and subsequently fertilized by the male. Following fertilization, the eggs are gathered into the buccal cavity for incubation. This incubation period may last a matter of a few weeks or as long as two months. During this time, the female does not eat. Once the eggs hatch, the young remain in the mother's buccal cavity until their yolk sacs are exhausted. During this period of infancy, the young fish do leave the mother's mouth for short periods which in some instances allows the mother to eat.
Obviously there are some disadvantages associated with this natural procedure. First, the female's inability to eat during the brooding period will cause her to lose substantial weight and not infrequently results in actual starvation. Furthermore, during this period, the female will not breed. Thus, the next brooding period is delayed. It has also been found that other fish will ram the brooding female causing eggs to be ejected from her buccal cavity. The ramming fish then quickly eat the expelled eggs. It is believed that the fish lay far more eggs than they are able to successfully breed and that many of the eggs are swallowed or expelled. It can be seen that many perils exist for both the female and the eggs under this natural method of brooding.
It has been found difficult to artifically brood the eggs of a mouthbrooding fish because the mouthbrooding technique provides many advantages along with the foregoing disadvantages. The eggs of a mouthbrooder require continual turning because the yolk of each egg would otherwise settle to the bottom. Such settling of the yolk results in the death of the embryo. The mouthbrooder female continually tumbles the eggs within her mouth to prevent this phenomenon. This tumbling action also keeps the eggs clean and prevents an infestation of bacteria. Mere containment within the mouth of the female also provides protection against bottom scavenging fish and other animals. Finally, the eggs may be kept in the proper temperature environment which the female naturally seeks.
Thus, the brooding process employed by mouthbrooding fish provides a number of both advantages and disadvantages for maximizing fish production. Some of the perils referred to above are also true for eggs of both egg layers and egg scatterers. Scavenging predators, bacterial infestation and external damage account for substantial losses of fish eggs in all varieties of fish brooding techniques.